The invention relates to a method for manipulating an audio equivalent signal, comprising positioning a chain of mutually overlapping time windows with respect to the audio equivalent signal on the basis of periodicity measurements of the audio equivalent signal so that a positional displacement between adjacent windows substantially corresponds to a principal period of said periodicity; and synthesizing an audio output signal by chained superposition of segment signals derived from the audio equivalent signal through weighting with the windows (i.e., an associated window function for each). Such a method has been described in earlier non pre-published European Application 91202044.3 (to which U.S. Pat. No. 5,479,564 corresponds), co-authored by the present inventors and assigned to the same assignee, which reference is incorporated herein by reference, inasfar as not actually included. Reference should also be made of a still earlier, pre-published reference, i.e., European Patent Application EP-A-363 233. The object of those references was to change the prosody for synthesized speech, the pitch of the output signal, and the duration of stretches of speech. In combination with the junior reference (i.e., European Application 91202044.3), the method should be performed automatically, be robust against noise, and retain a high audio quality for the output signal. The inventors of the present invention have realized that the manipulation of the duration can be used in various situations where there are external constraints to the total length of a self-contained unit of speech, which constraints may specify both the maximum and the minimum duration of such unit.